Expandable layer made of compressible material

ABSTRACT

An expandable layer made of compressible material placed in a rotary printing from between a core cylinder and a sleeve. An embodiment includes depressions on the outer circumferential surface and/or the inner circumferential surface of the expandable layer. The depressions can be, at least partly, fashioned as open circumferential annular channels. In addition, at least some of the depressions and annular channels can be arranged according to a required bending compensation of the sleeve. In another embodiment, an initial section of the depressions stretches in an axial direction on the expandable layer and a subsequent section of the depressions stretches in a radial direction over the expandable layer, whereby a part of the material of the expandable layer can be displaced in the depressions and at least a portion of the depressions is arranged according to a required bending compensation of the sleeve.

This application claims priority to German Application No. DE 199 18432.1, filed on Apr. 23, 1999, and PCT/DE00/01092 filed on Apr. 6, 2000,both of which are herein incorporated by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present invention relates generally to rotary printing formprocesses, and more particularly, to an expandable layer made ofcompressible material placed in a rotary printing form between a corecylinder and a sleeve.

2. Background of the Invention

Primarily two different rotary printing form processes are used in theprinting industry.

In the intaglio printing process metallic cylinders fitted with afunction profile on the surface are predominantly used. Usually, steelrollers are galvanically plated with a copper layer, which then carriesthe function profile.

In flexography printing, rotary printing forms, which have a sleevefitted onto a metallic roller core are often used. The sleeves are oftengalvanically made into, for example, nickel sleeves or consist of fiberreinforced thermoplastic materials. The function profile is located onthe outer surface of the sleeve.

Other technical areas use metallic cylinders with a technical surface,for example, coatings of polytetrafluoroethylene, which have ananti-adhesive effect, metallic sleeves or hollow cylinders with atechnical surface as well as rolled fiber reinforced thermoplasticsleeves with a technical surface. Similar to the manner in which thesleeves in flexography printing are attached, the technical sleevescould then be pneumatically attached to the roller core. They are alsoused as pipes or semi-finished products for cylinder production.

Sleeves are more and more often produced using thermoplastic pipes orflexible hoses or they are made of composites. The rubular semi-finishedproducts are attached or as the case may be lead onto a conical cylinderusing a heat source. This is described in further detail in theunpublished application DE 198 54 735.8. Non-conical productioncylinders, too, could be used for the sleeve production. After heatingthe production cylinder using, for example, a heat transporting liquidor a pre-connected heating process, the rubular semi-finished product ispushed onto the production cylinder using a force fit direction. It isalso possible to lead the semi-finished product directly from anextruder onto the production core. After the attachment process theproduction core is cooled so the thermoplastic material of the sleeveconsolidates. Depending on the adjustment of the production parameter,the post consolidation frozen tensile strengths can be adjusted in sucha manner that the sleeve remains on the production cylinder or that itwill be de-molded. The de-molding could occur with the help of, forexample, a scraper.

The de-molded sleeves could be placed on and removed from acorresponding core cylinder. This could occur pneumatically ormechanically. The connection of the sleeve to the core cylinder, whichis made of, for example, steel or synthetics, can occur using frictionalresistance or a mold clamping mechanism. When using a frictionalresistance connection, the sleeve is made on a production core, whichhas a slightly smaller diameter than the ultimate core cylinder. Theproduction core may also show the same deviations whereby the residualstress generated during the production is taken advantage of.

When using the mold clamping mechanism connection, the sleeves are madeon a production core, which is fined with geometric structures, forexample, grooves that are cast into the sleeves. The core cylindercarries the complimentary structure so that this combination willconstitute the mold clamping mechanism.

It has proven to be advantageous, as has been described in DE 198 34735, to provide the core cylinder or, as the case may be, also thesleeve with a compressible expandable layer. Should the sleeve materialnot show enough elasticity itself, such an expandable layer will have abalancing effect. This expandable layer is, in particular, necessarywhen the sleeve must be attached in a detachable union. It prevents thesleeve from being damaged by the high pressure during attachment andremoval. Furthermore, the use of an expandable layer can evenlydistribute the surface pressure on the sleeve. An expandable layer isalso necessary during de-molding using air to allow the air cushions tobe effective on the entire surface in order to ensure problem freeattachment and removal of the sleeve.

Furthermore, the expandable layer has the advantage that smallirregularities on, for example, the inner tubular surface of the maincasting do not have an effect on the sleeve since they are smoothed outlater on the core cylinder by the expandable layer. Expensive interiorwork such as honing is thus not necessary. It is also in this mannerthat other critical semi-finished products such as extrudedthermoplastic pipes or composite plastic pipes produced using pultrusioncan substitute for the sleeve. It remains an advantage that geometricstructures can be cast on the production cylinder during production.

In this manner the expandable layer on the one hand stores the force,which is necessary for the frictional resistance connection between thecore cylinder and the sleeve and provides the force locking between thetwo. Simultaneously, the surface pressure is evenly distributed.

As mentioned above, a function profile is introduced in the sleeve afterthe production process. This could occur through direct structuringusing a laser beam, through de-ionization or through mechanicalmachining. In a second process, coatings made of polyurethane,polytetrafluoroethylene, copper, and other such materials can bepositioned and will then be available as a functional layer. Flexographyprinting blocks may be directly attached. Depending on the ultimatepurpose, tubular main castings of different materials and sizes areused. The use of expandable layers allows the sleeve itself to have athick wall thickness so that it can only be slightly stretched.

The sleeve is used as a printing form for intaglio printing, flexographyprinting, or for embossing, and with the help of lasers mesh structuresmay also be introduced into the sleeve.

It can be used as a technical sleeve and would in that case be insertedwithout core cylinder.

The functional layer could also be, for example, a surface layerprotection.

The function profile also includes penetrations, perforations, and thelike through the sleeve. In this manner it is also possible to perforatethe sleeve as a sieve. Then such a sleeve could, for example, be used asa rotation sieve for the straining of bulk materials, or as a suctioncylinder, for example, for the removal of foils or for the draining ofwater from paper.

Due to the flexible character of the surface it may also be used as atextile-printing stencil.

EP 0 196 443 A2 discloses a sleeve with an inner layer made of anelastic rubber material and which is provided with circumferentiallyrunning channels on its outer surface. Forced-draft ducts are filledwith compressed air during attachment and have no influence on thecompressibility of the layer in which they are located. A similar sleeveis described in U.S. Pat. No. 4,864,926. Both sleeves must be attachedusing compressed air.

SUMMARY OF THE INVENTION

It can be concluded from the discussion above that the expandable layeris of particular importance. Therefore, it is the purpose of theinvention to make available an expandable layer, between a core cylinderand a rotary printing form, that better fulfills the task that confrontit, and through which especially a sleeve can be attached in an improvedmanner.

In an embodiment of the present invention this task is solved throughthe use of an expandable layer made of a compressible material, which isattached to a rotary printing form between a core cylinder and a sleeve.The expandable layer has depressions on its outer circumferentialsurface and/or inner circumferential surface.

In a further aspect of the present invention, the depressions arefashioned, at least partly, as open circumferential annular channels.

In a further aspect of the present invention, the annular channels arerun parallel to each other.

In a further aspect of the present invention, the annular channels areplaced equidistantly.

In a further aspect of the present invention, the depressions, at leastpartly, are fashioned as channels for use with liquid or gaseous media.

In a further aspect of the present invention, the expandable layer isfitted with surface layer protection on its outer circumferentialsurface.

In a further aspect of the present invention, the expandable layer ismade of an elastic material with gaseous filling, for example, plasticfoam or expanded polystyrene pellets.

In a further aspect of the present invention, the elastic materialand/or the surface protection layer is fined with electrical conductionparticles.

In a further aspect of the present invention, at least some of thedepressions or annular channels are arranged according so the requiredbending compensation of the sleeve.

In a further aspect, the present invention provides an expandable layermade of compressible material, which could be fitted to a rotaryprinting form between a core cylinder and a sleeve. Depressions arefitted on the outer circumferential surface or on the innercircumferential surface of the expandable layer. An initial section ofthe depressions stretches in an axial direction on the expandable layer.A subsequent section of the depressions stretches in a radial directionover the expandable layer, whereby a part of the material of theexpandable layer can be displaced in the depressions and at least aportion of the depressions is arranged according to a required bendingcompensation of the sleeve.

In a further aspect, the present invention provides a core cylinder withan expandable layer made of compressible material, which is adapted tobe attached to a rotary printing form between the core cylinder and asleeve. Depressions are fitted on the outer circumferential surface oron the inner circumferential surface of the expandable layer. An initialsection of the depressions stretches in an axial direction on theexpandable layer. A subsequent section of the depressions stretches in aradial direction over the expandable layer, whereby a part of thematerial of the expandable layer can be displaced in the depressions andat least a portion of the depressions is arranged according to arequired bending compensation of the sleeve.

In a further aspect, the present invention provides a rotary printingform with an expandable layer made of compressible material, which isattached to the rotary printing form between a core cylinder and asleeve. Depressions are fitted on the outer circumferential surface oron the inner circumferential surface of the expandable layer. An initialsection of the depressions stretches in an axial direction on theexpandable layer. A subsequent section of the depressions stretches in aradial direction over the expandable layer, whereby a part of thematerial of the expandable layer can be displaced in the depressions andat least a portion of the depressions is arranged according to arequired bending compensation of the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a preferred embodiment of a corecylinder with an attached expandable layer, during the attachment of asleeve, in accordance with the present invention.

FIG. 2 is a schematic diagram of a preferred embodiment of a sleevecompletely attached to the core cylinder, in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a cylindrical core cylinder 2 is shown with an expandablelayer 3 attached. This expandable layer is provided with severaldepressions 4 on its outer circumferential surface, which in this caseare fashioned as open circumferential annular channels. The expandablelayer 3 can be fitted with surface layer protection on the outersurface, which however is not shown. A sleeve 1 is attached to the corecylinder 2 and the expandable layer 3 from the left in the drawing. Tofacilitate the attachment a channel 5 is running through the corecylinder 2 and expandable layer 3, over which the sleeve 1 can becharged on with pressure, which could, for example, be generated using agaseous medium. FIG. 1 clearly shows that those areas of the expandablelayer 3, which are already under the sleeve 1, are very compromised,whereby a part of the expandable layer material is displaced in thedepressions 4.

FIG. 2 shows the completely attached sleeve.

In accordance with an embodiment of the invention, the outer or theinner circumferential surface of the expandable layer is provided withdepressions. The depressions could stretch in axial and/or radialdirection over the expandable layer and could have different shapes andcross sections. They could also be shaped as holes that, for example,could continue hole structures in the sleeve through the expandablelayer. At least a part of the depressions, which are also shaped as opencircumferential annular channels, are fashioned in accordance with arequired bending compensation of the sleeve.

During the attachment of the sleeve, a part of the expandable layermaterial is displaced in the depressions so that the compressibility ofthe expandable layer increases. Depending on the distribution, shape,and geometric arrangement of the depressions the sleeve bending could becompensated for.

In accordance with an embodiment of the present invention, thedepressions are, at least in part, shaped as open circumferentialannular channels. The annular channels could run parallel to each other.

Another embodiment provides annular channels that are arrangedequidistantly; should the bending compensation require otherwise, agrouping of annular channels in which the annular channels are placedrelatively closely together is also possible.

The depressions could, at least partly, be fashioned to accommodateliquid or gaseous media, which could, for example, be used to heat orcool the sleeve. The channels could also be spray or suction channelsfor color.

It has proven useful to equip the expandable layer with surface layerprotection on the outer circumferential surface. This ensures a longerlifespan for the expandable layer in particular when the sleeve is oftenexchanged.

In an embodiment of the present invention, the expandable layer is madeof an elastic material with gaseous filling, for example, plastic foamor expanded polystyrene pellets.

In another embodiment, for some uses, the elastic material and/or thesurface layer protection is fitted with electrical conduction particles.

The re-designed expandable layer allows other functions to beimplemented whereby it is still placed on the core cylinder or as thecase may be on the inner side of the sleeve, to serve as an improvedcompensation layer which precisely sets up the contact line, forexample, between the sleeve and an impression cylinder in a flexographyprinter.

In another embodiment, the invention provides a core cylinder with anexpandable layer made of compressible material, which could be attachedto a rotary printing form between the core cylinder and a sleeve, fittedwith depressions on the outer circumferential surface or on the innercircumferential surface of the expandable layer, whereby an initialsection of the depressions stretches in axial direction on theexpandable layer and whereby a subsequent section of the depressionsstretches in radial direction over the expandable layer, whereby a partof the material of the expandable layer can be displaced in thedepressions and at least some of the depressions are arranged accordingto a required bending compensation of the sleeve.

In another embodiment, the invention provides a rotary printing formwith an expandable layer made of compressible material, which isattached to a rotary printing form between a core cylinder and a sleeve,whereby the expandable layer is fitted with depressions on its outercircumferential surface or on its inner circumferential surface, wherebyin accordance with the invention an initial section of depressionsstretches in axial direction on the expandable layer and whereby asubsequent section of the depressions stretches in radial direction overthe expandable layer, whereby a part of the expandable layer materialcan be displaced in the depressions and at least a portion of thedepressions is arranged according to a required bending compensation ofthe sleeve.

The invention characteristics disclosed above and in the drawings aswell as in the claims could be significant both individually and in anychosen combination for the implementation of the invention.

The foregoing disclosure of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be obvious to oneof ordinary skill in the art in light of the above disclosure. The scopeof the invention is to be defined only by the claims appended hereto,and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

What is claimed is:
 1. A rotary printing form with an expandable layermade of compressible material, which is attached to a core cylinderbefore being inserting into a sleeve, wherein the expandable layer hasseparate recessed depressions on at least one of its outercircumferential surface and its inner circumferential surface, andwherein when the core cylinder with the expandable layer is insertedinto the sleeve, an initial section of the depressions stretches in anaxial direction on the expandable layer, and a subsequent section of thedepressions stretches in a radial direction over the expandable layer,whereby a part of the material of the expandable layer can be displacedin the depressions and at least a part of the depressions provideschannels between the expandable layer and the sleeve when the sleeve isattached to the core cylinder and the expandable layer.
 2. A corecylinder with an expandable layer made of compressible material, theexpandable layer adapted to be attached to a rotary printing formbetween the core cylinder and a sleeve, wherein the expandable layer hasseparate recessed depressions on at least one of its outercircumferential surface and its inner circumferential surface, andwherein when the core cylinder with the expandable layer is insertedinto the sleeve, an initial section of the depressions stretches in anaxial direction on the expandable layer, and a subsequent section of thedepressions stretches in a radial direction over the expandable layer,whereby a part of the material of the expandable layer can be displacedin the depressions and at least a part of the depressions provideschannels between the expandable layer and the sleeve.
 3. An expandablelayer comprising a compressible material, the expandable layer beingattached to a core cylinder before inserting into a sleeve, wherein theexpandable layer has separate recessed depressions on at least one ofits outer circumferential surface and inner circumferential surface,wherein the recessed depressions are, at least partly, fashioned as opencircumferential annular channels, and wherein when the core cylinder andthe expandable layer are inserted into the sleeve, the expandable layeris between the sleeve and the core cylinder, and at least a part of therecessed depressions provides channels between the expandable layer andthe sleeve.
 4. The expandable layer of claim 3, wherein the annularchannels run parallel to each other.
 5. The expandable layer of claim 3,wherein the annular channels are placed equidistantly.
 6. The expandablelayer of claim 3, wherein the depressions are, at least partly,fashioned as channels for use with one of liquid media and a gaseousmedia.
 7. The expandable layer of claim 3, wherein the expandable layeris made of an elastic material with gaseous filling.
 8. The expandablelayer of claim 7, wherein the elastic material is one of plastic foamand expanded polystyrene pellets.
 9. The expandable layer of claim 7,wherein the elastic material is fitted with electrical conductionparticles.
 10. An expandable layer comprising compressible material,which is attached to a core cylinder before inserting into a sleeve,wherein the expandable layer has separate recessed depressions on atleast one of its outer circumferential surface and inner circumferentialsurface, wherein the depressions are, at least partly, fashioned as opencircumferential annular channels, and wherein when the core cylinder andthe expandable layer are inserted to the sleeve, at least some of thedepressions and annular channels of the expandable layer are arranged tocompensate for a bending of the sleeve, and at least a part of therecessed depressions provides channels between the expandable layer andthe sleeve.
 11. The expandable layer of claim 10, wherein the annularchannels run parallel to each other.
 12. The expandable layer of claim10, wherein the depressions are, at least partly, fashioned as channelsfor use with one of a liquid media and a gaseous media.
 13. Theexpandable layer of claim 10, wherein the expandable layer is made of anelastic material with gaseous filling.
 14. The expandable layer of claim13, wherein the elastic material is one of plastic foam and expandedpolystyrene pellets.
 15. The expandable layer of claim 13, wherein theelastic material is fitted with electrical conduction particles.
 16. Anexpandable layer comprising compressible material, adapted to be fittedto a rotary printing form between a core cylinder and a sleeve, whereinthe expandable layer is attached to the core cylinder and has separaterecessed depressions fitted on at least one of its outer circumferentialsurface and inner circumferential surface, wherein when the corecylinder and the expandable layer are inserted into the sleeve, aninitial section of the depressions stretches in an axial direction onthe expandable layer, and a subsequent section of the depressionsstretches in a radial direction over the expandable layer, whereby apart of the material of the expandable layer can be displaced in thedepressions and at least a part of the depressions provides channelsbetween the expandable layer and the sleeve.
 17. The expandable layer ofclaim 16, wherein the depressions of the subsequent section ofdepressions at least partly are fashioned as circumferential openannular channels running in a radial direction and which are arrangedrunning parallel to each other.
 18. The expandable layer of claim 16,wherein the depressions at least partly are fashioned as channels foruse with one of liquid media and gaseous media.
 19. The expandable layerof claim 16, wherein the expandable layer is made of an elastic materialwith gaseous filling.
 20. The expandable layer of claim 19, wherein theelastic material is one of plastic foam and expanded polystyrenepellets.
 21. The expandable layer of claim 19, wherein the elasticmaterial is fitted with electrical conduction particles.